%% Copyright (C) 2009 Muthiah Annamalai <muthuspost@gmail.com>
%%
%% This program is free software; you can redistribute it and/or
%% modify it under the terms of the GNU General Public License
%% as published by the Free Software Foundation; either version 2,
%% or (at your option) any later version.
%%
%% This program is distributed in the hope that it will be useful,
%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%% GNU General Public License for more details.
%%
%% You should have received a copy of the GNU General Public License
%% along with this program; If not, see <http://www.gnu.org/licenses/>.

## Usage:
## 
## xt = sampled2continuous( xn , T, t )
## 
## Calculate the x(t) reconstructed
## from samples x[n] sampled at a rate 1/T samples
## per unit time.
## 
## t is all the instants of time when you need x(t) 
## from x[n]; this time is relative to x[0] and not
## an absolute time.
## 
## This function can be used to calculate sampling rate
## effects on aliasing, actual signal reconstruction
## from discrete samples.
## 
function xt = sampled2continuous( xn , T, t )
  if ( nargin < 3 )
    print_usage()
  endif
  
  N = length( xn );
  xn = reshape( xn, N, 1 );
  [TT,tt]= meshgrid(T*(0:N-1)',t);
  S = sinc((tt -TT)./T);
  xt = S*xn;
  return
end
